Dopamine receptors belong among G-protein-coupled receptors that are expressed in the central nervous system. Dopamine receptors are classified into dopamine D1 receptor-like family and dopamine D2 receptor-like family. Among dopamine receptors, dopamine D1 and D5 receptors belong to the dopamine D1 receptor-like family, and dopamine D2, D3, and D4 receptors belong to the dopamine D2 receptor-like family.
It has been reported that the dopamine D1 receptor is coupled with Gs, which is a promoting G protein, to activate an adenylate cyclase, and enhances the production of cAMP in a cell to promote protein kinase A activity, and exhibit various functions (Medicinal Research Reviews, 2009, vol. 29(2), p. 272-294).
There is a report suggesting that the reduction of the dopamine D1 receptors in the prefrontal cortex plays an important role in cognitive impairment and schizophrenia negative symptom. Because in patients with schizophrenia, dopamine D1 receptors were significantly reduced in a part of the frontal lobe, called a prefrontal cortex. Furthermore, because the degree of reduction of the dopamine D1 receptors was correlated with the results of Wisconsin Card Sorting Test which is a test for the intensity of schizophrenia negative symptom and the function of the frontal lobe (Nature, 1997, vol. 385(6617), p. 634-636).
Even in patients with depression, similarly to patients with schizophrenia, functional impairment in the prefrontal cortex has been reported (Psychiatry Research, 1999, vol. 89, p. 171-187).
It has been reported that, in a cognitive impairment model, a dopamine D1 receptor agonist is useful (European Neuropsychopharmacology, 2009, vol. 19(6), p. 440-450; Psychopharmacology, 2010, vol. 210(3), p. 407-418; Molecular Pharmacology, 2007, vol. 71(6), p. 1598-1609; and Annals of the New York Academy of Sciences, 1996, vol. 777, p. 427-430).
It has been reported that a dopamine D1 receptor is related to schizophrenia negative symptom (The American Journal of Psychiatry, 2002, vol. 159(5), p. 761-767; and Pharmacopsychiatry, 2006, vol. 39(3), p. 115-116).
Therefore, the dopamine D1 receptor agonist is expected as a drug that stimulates the dopamine D1 receptor in the prefrontal cortex and can ameliorate cognitive impairment, schizophrenia negative symptom, CIAS, and depression.
There is a report suggesting that the dopamine D1 receptor agonist is expected to be applied to Parkinson's disease (Current Opinion in Investigational Drugs, 2001, vol. 2(11), p. 1582-1591) and Alzheimer's disease (The Journal of Biological Chemistry, 2011, vol. 286(5), p. 3270-3276).
Further, the dopamine D1 receptor agonist has been reported to exhibit the efficacy in each animal model of Huntington's disease (Neurodegenerative Diseases, 2011, vol. 8(4), p. 230-239) and drug dependency (Neuroscience Letters, 2012, vol. 513(2), p. 214-218).
Moreover, it has been suggested that a dopamine agonist is expected to be applied to cognitive impairment in ADHD (Neuropsychologia, 2013, vol. 51(2), p. 235-266; and Pharmacogenomics and Personalized Medicine, 2014, vol. 7, p. 349-356).
Therefore, a compound stimulating the dopamine D1 receptor is expected to be promising as an agent for preventing and/or treating diseases such as cognitive impairment, schizophrenia negative symptom, CIAS, Parkinson's disease, Alzheimer's disease, Huntington's disease, depression, ADHD, drug dependency, or the like.
The dopamine D1 receptor agonist is also used as an antihypertensive agent of peripherals (The New England Journal of Medicine, 2001, vol. 345(21), p. 1548-1557). Meanwhile, for example, it has been reported that dihydrexidine, which is a dopamine D1 receptor agonist that had been developed for Parkinson's disease, causes blood-pressure reduction as a side effect although exhibiting efficacy in Parkinson's disease (Clinical Neuropharmacology, 1998, vol. 21(6), p. 339-343).
Therefore, a compound that stimulates a dopamine D1 receptor but has no side effect, such as a blood-pressure reduction, is expected to be created.
A G-protein-coupled receptor has been long researched as an important target for drug discovery. In recent years, it has been revealed that many G-protein-coupled receptors also have allosteric sites different from orthosteric ligand sites (ACS Chemical Biology, 2008, vol. 3(9), p. 530-541). Here, research for drug discovery, in which allosteric sites in G-protein-coupled receptors are targets for drug discovery, has actively been made (British Journal of Pharmacology, 2012, vol. 165(6), p. 1659-1669).
A positive allosteric modulator (hereinafter, referred to as PAM) is a compound that binds to a site different from a binding site of an endogenous ligand to enhance a receptor function. PAM does not enhance a receptor function in itself, but enhances the receptor function in the presence of a ligand.
Therefore, it is expected that a dopamine D1 receptor PAM (hereinafter, referred to as D1 PAM) has a PAM action on a dopamine D1 receptor, can be used for preventing and/or treating cognitive impairment, schizophrenia negative symptom, CIAS, Parkinson's disease, Alzheimer's disease, Huntington's disease, depression, ADHD, drug dependency, or the like, and is useful as a drug with less side effects compared to a dopamine D1 receptor agonist.
It is reported in Patent Document 1 that a compound of the formula (A) has a benzodiazepine (03 receptor agonist action. In claims, an anti-anxiety agent or anti-depressant agent is described.

(In the formula, R1 and R2 form a saturated heterocyclic group which may be substituted together with a nitrogen atom to which they are bonded. However, (1) in the case of the following (a) or (b), R1 and R2 do not form a saturated heterocyclic group which may be substituted together with a nitrogen atom to which they are bonded. In (a), all of R5, R6, R7, and R are hydrogen atoms. In (b), one or two of R5, R6, R7, and R8 are each independently halogen atoms, and the others are hydrogen atoms. X represents O, S, NR10, or CR11R12. Refer to this publication for the other symbols.)
It is reported in Patent Document 2 that a compound of the formula (B) has urotensin II antagonist and inhibition actions, and is useful in congestive heart failure or the like.

(Refer to this Publication for the Other Symbols.)
It is reported in Patent Document 3 that a compound of the formula (C) has cannabinoid 1 antagonist and/or inverse-agonist actions, and is useful as a central functional agent or the like.

(In the formula, each of R1 and R2 is alkyl, cycloalkyl, aryl, aryl-alkyl, heteroaryl, heteoaryl-alkyl, or the like. Refer to this publication for the other symbols.)
It is reported in Patent Document 4 that a compound of the formula (D) is useful in the treatment and/or prevention of dyskinesia and/or movement fluctuation.

(In the formula, each of R3 and R3a is H or unsubstituted C1-4 alkyl. Refer to this publication for the other symbols.)
It is reported in Patent Document 5 that a compound of the formula (E) is useful in the treatment and/or prevention of schizophrenia.

(Refer to this Publication for the Other Symbols.)